1. Technical Field
The present disclosure relates to environmental odor control technology. In particular, the disclosure relates to zeolite composite products for waste odor control applications, such as landfills and composting.
2. Summary of Related Art
Sanitary landfills are sources of hydrogen sulfide, greenhouse gases, and more than 100 non-methane organic compounds (NMOCs) of which over 30 are designated as hazardous air pollutants. A principle class of odorous compounds emitted from landfills is sulfur-based gases (Paraskaki et al., Waste Management and Research 23:199-208 (2005); Dincer et al., J. Chromatog. A 1122:222-229 (2006)). For example, hydrogen sulfide is a toxic gaseous compound that forms a primary component of emissions from solid waste sites. Landfill caps are used to control the emissions of such gases once the landfill is at maximum grade. However, prior to reaching the grade for capping, a landfill needs to have a daily cover applied.
Traditional daily covers for landfills consist of soil applied to the surface; however this is a labor intensive process which consumes valuable landfill space. Owners and operators of municipal solid waste landfills (MSWLF) typically are required to cover disposed solid waste with 30 cm of earthen material at the end of each day of operation. More frequent applications of earthen material may be necessary to control fire hazards, blowing litter, odors, insects, vectors, and rodents (Haughy, Waste Management Research 19:89-95 (2001); ASTM Standard Designation D6523, Standard Guide for Evaluation and Selection of Alternative Daily Covers (ADCs) for Sanitary Landfills (2005); Ohio EPA Guidance Document #0654, OAC Rule 3725-27-19 (Nov. 2, 2004)). It is also required that waste not be uncovered or exposed for more than 24 hours after unloading.
Other options or alternatives to the daily cover have been approved. Alternative Daily Covers, or ADC's, are primarily valued for their ability to conserve airspace by reducing the soil cover needed for landfills. ADCs fall into two major categories: tarps and spray-on materials. The various spray-on ADCs include foam, mulch, and slurries which harden after application. Each of these alternatives provides adequate cover while freeing up hundreds of cubic yards of space per ½ acre working face. The major cost savings for ADCs is realized by extending the life of the landfill; however, this can be offset by materials and application cost for the ADC.
Tarp or blanket ADCs can be reusable or nonreusable. Reusable types are commonly constructed of polypropylene or polyethylene and are deployed and weighted down for overnight use, then retracted each morning. Reusable blanket ADCs are designed to be puncture and tear resistant. Nonreusable ADCs are commonly composed of thin polypropylene, polyethylene, or polyvinyl chloride. Some nonreusable ADCs are thermally degradable and last from about 4 to 6 weeks. Other nonreusable ADCs are more resistant to degradation and are perforated so that the blanket ADC does not act as an impervious membrane. Tensile strength is also consideration in designing an ADC, although requirements can vary greatly and depend on the method of application and characteristics of the MSWLF. Reusable ADCs that are mechanically deployed and retracted typically are designed to be tough and durable. However, tensile strength is less important for a non-reusable ADC that is deployed and left in place.
There are two categories of spray ADCs, foams and slurries. Resin or soap commonly is mixed with water to create foam. Specialized spray equipment can then be utilized to apply the foam to the surface of the landfill. This forms a thin layer over the waste that does not harden. Spray application with no “shadowing” may require additional applications from various directions to ensure a thin, even layer. Foams do not need to be removed; they reduce to almost nothing as layers of waste are placed upon them. Slurry-based ADCs typically are created by mixing solid material with water and spraying the mixture on the working face of the landfill. Specialized hydro seeding equipment is typically necessary for application of the slurries. Spray ADCs have the advantage of limiting the loss of landfill volume by taking the place of 6 or more inches of soil as an odor control measure. Conserving space extends the life of the landfill, thereby making the landfill more cost effective. However, spray ADCs typically require the additional costs of leasing or purchasing specialized equipment and the maintenance of this equipment to apply the ADC.
In addition to landfills, waste and odor control issues are addressed in the context of composting by individual homeowners and larger scale organic waste producers, such as retail supermarket chains. In view of our society's rising environmental consciousness, a need exists for an alternative daily cover that is effective in the reduction of odors from landfills, composting facilities and other waste.